[Biological monitoring of treatment with low molecular weight heparin]

The monitoring of low molecular weight heparins (LMWH) can be realized in plasma from treated patients by measuring the anti-Xa activity. The commercially available methods belong to two different categories respectively measuring residual F Xa using clotting or amidolytic methods. The latter may be standardized and provided an appropriate standard is used present acceptable in laboratory variability. These chromogenic substrate based assays have been used in most clinical trial, thus have well known usual ranges. In most cases, it does not seem necessary to perform a biological test in prophylactic treatments. However in curative treatment the anti-Xa activity may help in evaluating the patient sensitivity and allowing a dose adjustment.